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Who wants to go and build a system in Elixir?

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Can't go out and rewrite it all

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You shouldn’t

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Elixir, your Monolith and You (alpha-1) Tobias Pfeiffer @PragTob pragtob.info

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Your Monolith and You

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Your Monolith now?

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Your Monolith?

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Tear it all down and rewrite it

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Sooooon!

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“We rewrote it all in Language x, now it’s 10 times faster and only 50% of the code!” Someone

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“Language x, is 10 times faster and requires 50% of the code of language Y!” Someone Often implies...

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What nobody tells you...

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Business Value?

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Sooooon!

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Replace it step by step

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We have a bedroom, for the bathroom please check out legacy!

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Terraform allows you to incrementally transform an older API into one powered by Phoenix - one endpoint at a time. poteto/terraform

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defmodule MyApp.Terraformers.Foo do alias MyApp.Clients.Foo use Plug.Router plug :match plug :dispatch get "/v1/hello-world", do: send_resp(conn, 200, "Hi") get _ do res = Foo.get!(conn) send_response({:ok, conn, res}) end end poteto/terraform

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Replace a critical component

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Check out our sweet new heating system!

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Write a new component

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Check it out we built a brand new high tech entertainment facility!

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Write a new component Obvious in microservices

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“Is the technology I’m choosing the right fit for the problem I’m trying to solve?” Everyone, hopefully

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Reasonably separate and limited problem

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Requirement that poses a problem for the current stack

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Spark of Enthusiasm

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Courier Tracking

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Courier Tracking

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Courier Tracking

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Courier Tracking Websockets

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Courier Tracking Websockets Basic Knowledge

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How to make them talk?

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Monolith Frontend Courier DB

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Monolith Tracking Frontend Courier DB DB

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Connect them?

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Monolith Tracking Frontend Courier DB DB

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JSON Web Token

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Header Payload Signature

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{ "role": "admin", "courier_ids": [1337, 55], "id": 42, "exp": 1520469475 }

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Monolith Tracking Frontend Courier DB DB Shared Secret

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Monolith Tracking Frontend Courier DB DB JWT JWT Shared Secret

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Monolith Tracking Frontend Courier DB DB JWT JWT JWT Shared Secret JWT

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def connect(%{"token" => token}, socket) do token |> JWT.verify_token |> respond_based_on_token_contents(socket) end Socket

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defp login_user(%{"role" => role, ...}, socket) do {:ok, assign(socket, :user, %{role: role, ...})} end Socket

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def join("courier:" <> courier_id, _, % {assigns: %{user: user}}) do if authorized?(courier_id, user) do # login else # unauthorizd end end Channel

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defp authorized?("", _), do: false defp authorized?(courier_id, %{courier_ids: ids}) do Enum.member?(ids, String.to_integer(courier_id)) end defp authorized?(_, _), do: false Channel

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Monolith Tracking Frontend Courier DB DB Locations Locations Most of the time

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Fulfillment

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Fulfillment CRUD

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Fulfillment CRUD Experience

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Monolith Fulfillment DB DB

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Monolith Fulfillment DB DB Own UI

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Monolith Fulfillment DB DB OAuth OAuth

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Monolith Fulfillment DB DB /current_user Who?

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Monolith Fulfillment DB DB Products

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Monolith Fulfillment DB DB Order Valid? Order

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Monolith Fulfillment DB DB Packaging Create

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Rail-way oriented programming!

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Railway Oriented Programming

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defmodule Fulfillment.OrderCreation do def create(params, customer, auth) do with {:ok, order} <- validate_order(params, customer), {:ok, order} <- validate_in_backend(order, auth), {:ok, order} <- Repo.insert(order) do {:ok, order} else {:error, changeset} -> {:error, changeset} end end end

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defmodule Fulfillment.OrderCreation do def create(params, customer, auth) do with {:ok, order} <- validate_order(params, customer), {:ok, order} <- validate_in_backend(order, auth), {:ok, order} <- Repo.insert(order) do {:ok, order} else {:error, changeset} -> {:error, changeset} end end end Validate internally

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defmodule Fulfillment.OrderCreation do def create(params, customer, auth) do with {:ok, order} <- validate_order(params, customer), {:ok, order} <- validate_in_backend(order, auth), {:ok, order} <- Repo.insert(order) do {:ok, order} else {:error, changeset} -> {:error, changeset} end end end Validate externally

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defmodule Fulfillment.OrderCreation do def create(params, customer, auth) do with {:ok, order} <- validate_order(params, customer), {:ok, order} <- validate_in_backend(order, auth), {:ok, order} <- Repo.insert(order) do {:ok, order} else {:error, changeset} -> {:error, changeset} end end end Save

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defmodule Fulfillment.OrderCreation do def create(params, customer, auth) do with {:ok, order} <- validate_order(params, customer), {:ok, order} <- validate_in_backend(order, auth), {:ok, order} <- Repo.insert(order) do {:ok, order} else {:error, changeset} -> {:error, changeset} end end end Done

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defmodule Fulfillment.OrderCreation do def create(params, customer, auth) do with {:ok, order} <- validate_order(params, customer), {:ok, order} <- validate_in_backend(order, auth), {:ok, order} <- Repo.insert(order) do {:ok, order} else {:error, changeset} -> {:error, changeset} end end end Error

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No Kafka/Message Queue?

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Be careful with new technologies!

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Microservices!

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Microservices! ”Macroapplications”

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All challenges are clearly technical

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All challenges are clearly technical

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Stakeholders

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Your team

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First Major Version

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Get the others on board

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Workshops

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To know it, you got to build it

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Pair Adopter with Alchemist

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Pair Adopter with Alchemist Alchemist doesn’t touch keyboard

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Knowledge

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Knowledge

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“We are still using this like Rails – we should use GenServers!” Someone on your team

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You don’t need to kill your Monolith, Complement it

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Your Apps

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Enjoy using Elixir effectively to help your company Tobias Pfeiffer @PragTob pragtob.info